Conventional breaking switches usually include fuses, and are generally of complicated structure. A space within the switch must be provided to accommodate the fuse. In earlier types of breaking switches, the fuse was made of zinc. When the switch was overloaded, the fuse would melt. The dripping zinc created the possibility of a short circuit and presented a danger to the user. More recently, a type of fuseless breaking switch has been utilized. Such a switch can be used to protect the circuit from overload, but is not capable of cutting off the power in case of a fire, when it is imperative that the power is interrupted.
As already been taught by the variety publications of the related field about the fuseless breaking switch, one U.S. Pat. No. 5,262,748 is taken into consideration as the most related one to the present invention.
The patent (see FIG. 1 and FIG. 2) mainly is about a fuseless breaking switch comprising a casing 1, a pressure sensitive button 21 mounted at the center of casing 1, and a pair of electrically conductive prongs 3 and 3', wherein, when the button 21 is depressed, it urges rod 23 and consequently the alloy plate 25 downward, and the downward movement of rod 23 will then be held in depressed position by the spring blade 24. Because the alloy plate 25 is fixed in a slot in casing 1, the plate 25 becomes slightly arched when influenced by the downward movement of the rod 23, thus complete the circuit between prongs 3 and 3' and also when the button 21 is released from its depressed position, the rod 23 would again rise to the position where the circuit is open.
Nevertheless, this patent has a problem which it is not able to fit in all kinds of current, voltage supply, especially whenever the circuit is overloaded, the switch will either too easily or hard to cut off the current supply.